they can get about 3/4" to an 1" in diameter. i have had these in my tank from day one and never had any problems until i got this new one. the new one eats my star polyps, hacked of my coral banded shrimps arms, ate my xenia, and knocks just about every frag
off of every shelf in my tank.
so he's making me a little angry but i can't catch the little guy to bring him back to the lfs